A database schema of a database system is the database's structure described in a formal language supported by the database management system (DBMS). The database schema refers to the organization of data as a blueprint of how a database is constructed. A database schema is a set of formulas (sentences) often referred to as integrity constraints imposed on a database. These integrity constraints may ensure compatibility between parts of the schema. All constraints are expressible in the same language. When a developer develops a software using a database, several versions of the database schema may exist either during the development life cycle of the database as well as when the database is in production in a customer environment.